Quo warranto challenges someone's right to hold office or exercise a franchise — a very different question from mandamus.

Quo warranto, Latin for "by what authority," is another of the historical prerogative writs, used to challenge a person's or entity's legal right to hold a public office, franchise, or corporate charter.

What quo warranto actually asks

A quo warranto action asks a court to determine whether someone occupying a public office or exercising some governmental franchise actually has the legal authority to do so — for example, challenging whether someone was validly elected or appointed, or whether a corporation is exceeding the authority granted by its charter.

How this differs from mandamus

Mandamus assumes the respondent legitimately holds their position and simply is not performing a required duty. Quo warranto, by contrast, challenges whether the respondent has any legitimate claim to the position or authority at all.

Who typically brings a quo warranto action

In most jurisdictions, quo warranto actions are brought by the state itself, often through the attorney general, though some states allow a private citizen to request that the attorney general bring the action, or to bring it directly in limited circumstances.

Modern usage

Quo warranto has become considerably less common than mandamus in everyday litigation, but it still appears in disputes over contested elections to public or corporate office, and in challenges to whether an official continues to hold a position after a term has expired or a disqualifying event has occurred.

Practical significance for petitioners

Anyone who believes an official's very authority to act — not merely their failure to perform a duty — is the real problem should evaluate whether quo warranto, rather than mandamus, is the more appropriate remedy.